Okay so this isn't an airplane, it does have a propeller though :-)
I know, technically this doesn't belong on this forum but I thought those that enjoyed my other build threads might get a kick out of this.

So anyway I thought I'd have some fun & scratch build myself an airboat from crashed plane parts. I did some research, looked at lots of airboat designs then sat down at the computer & designed myself a boat...

Here's a collection of parts I found laying around the work shop...

no name 3536 800 kv motor (it used to haul around a 55" Piper Cub)

45a car ESC with reverse (might be nice to be able to backup)

el-cheapo servo (19g / 2.5kg / .14sec)

el-cheapo 6 channel receiver (way too many channels I know)

lipo battery (I have lots of sizes)

gyro (single axis)

Reverse?
This boat may see some service as a rescue boat for downed seaplanes so I want to be able to reverse to make that job easier. For the most part this boat will be used to screw around with when I'm not flying though.

Gyro?
Not sure she'll need this but I've been itching to use this gyro in a project. I know airboats can be pretty squirly so I may mess around with a little gyro stabilization fun.

Anyway lets get to the buildI printed up a set of templates from my design...

As she's only a baby airboat, I'm using 5mm DollarTree foam-board for the majority of this build. Contact cemented the templates to the foam-board...

A laser cutter would have been nice but I don't mind doing things old school. An hour or so of hand-cutting & we have a set of parts...

In addition to the foam-board, I am using some lite-ply to beef up where the motor pylon will mount...

Adding the foam-board parts...

More progress...

Starting to look a tad boat-like...

Got the bulk of the bottom sheeted...

I'm using a plastic Chinese takeout container for my radio box. It weighs almost nothing, is water proof (tested to make sure) & it has a lid that's easy to pop on/off...

I agree a rescue-cam would be fun. My GoPro camera comes with a water proof casing so no worries about it getting wet.

Yes a prop-guard would make sense for a rescue boat, pretty sure most folks don't want you chewing up their plane with the prop. I'm actually thinking I'll use a floating frame rig (PVC piping with foam insulation) to do my rescuing. Something like this...

The idea being this is used only when needed, the rest of the time she's a regular airboat. The rig is made from PVC pipe & foam pipe insulation...

I'm thinking with that setup, I can probably get away without needing a prop guard, maybe *shrug*.

That's one whacky looking fin there Soarrich. Not sure if I like it or not but if it works, that's pretty cool. I guess my only question would be, why don't most airboats have them?

Its a little early to be talking plans Scott. Lets see if she floats first. If she's successful though, sure I can see me making plans available. And to answer your other question, my boat is a tad over 20" (50cm) long.

Back to the build
I'm learning, working with foam-board, its all about beveling...

Rough shape for the side...

Glued on, trimmed & yeap, more beveling...

These two blocks will be used to mount the motor pylon...

I chose a bolt-on system so that I can remove the motor pylon if it gets damaged or if I want to try something different on there...

A little plywood crash protection up front...

The deck...

Added some weight while the glue dries, the pillow helps evenly distribute the weight...

She's looking kinda boat-like...

7.5 oz (212 g) not sure if that's good or bad for a vessel this size. Feels pretty light to me but there's lots more to add before we're done...

It looks like you have retained the paper on the foamboard. If so, you have be sure to seal the hull inside and out real good from any water. If you dont any water that gets to the paper will start it to de-laminate from the foam core and you will have a big mess and it will probably start to fall apart. I built a large "MUD-Duck" like plane out of the stuff and left the paper on it and after a while just the dew from the grass got to it and it slowly de- laminated the paper....

This should be fun. I made something roughly similar when I was a lad (that's looong ago!) with a glow motor up top. I made it too light and narrow, the torque of the motor used to capsize it. You might want to leave an option to add ballast in the sides? It much depends on how much power you are putting through the motor of course, and your design is wider than mine was so should be more stable, plus the battery will act as ballast, so probably it will be fine.

Ballast is a thought. Yeah if need be I could add some under the radio box. I guess we'll have to see how she handles.

Originally Posted by soar-ne

It looks like you have retained the paper on the foamboard. If so, you have be sure to seal the hull inside and out real good from any water. If you dont any water that gets to the paper will start it to de-laminate from the foam core and you will have a big mess and it will probably start to fall apart. I built a large "MUD-Duck" like plane out of the stuff and left the paper on it and after a while just the dew from the grass got to it and it slowly de- laminated the paper....

Bob M.

You had to bring up the paper issue LOL. Yeap I'm already regretting leaving it on there. Check out what happened today...

Build logs that go smoothly are boring
My fancy DollarTree foam-board has a paper covering. As this is a boat it's obviously gonna get wet... paper Vs water = bad. I wasn't too concerned however as I intended to fiberglass everything...

About halfway though wetting the fiberglass (brushing on the epoxy resin) I started to run low on resin. No worries, I quickly mixed up a second batch & finished her off. An hour later when I checked to see how she was looking, I noticed this big honking wrinkle...

The paper had swelled & buckled exactly where I'd stopped to mix up the second batch. Ugg! So after she'd cured I cut out the bump & laid over some fresh glass. I can't believe I'm patching the hull already LOL...

That should sand out just fine but geesh what a pain.

Wanting to avoid any new unpleasantness with the paper I removed all the paper from the top deck before glassing that. Although the foam-board gets most of its strength from the paper covering I figure it should be plenty strong with fiberglass on there instead...

I used to use Foam Board, But i got Spoiled Real Quick when i started useing 6mm Depron I also like the Great Planes pro Formance Foam, its seems to be just like Depron and it does not cost that much. I figure if your going to spend the time in building a Model, might as well use a Quality product for best results, just my 2 cents worth, Take care, Chellie

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL

I started using this DollarTree foam-board after watching Ed do his thing over at Experimental Airlines. He's had great success using this stuff.

Yeah sure I could buy expensive foam but at just $1 for a 20" x 30" sheet, I'm far more likely to experiment & have fun building goofy stuff than I would using the expensive foam. Besides this stuff is really pretty good. I'm quite impressed.

Stock with the paper on both sides, its very rigid. Remove one side & you can bend it into nice curved shapes. Take both sides off & you more or less have a sheet of crash-proof EPP kinda stuff. Its pretty versatile & unlike other foam-board, the paper peels off in one piece.

I picked up 20 sheets, enough for dozens of projects, for just $20. Gonna have some fun with it & see what I think. I'll save the expensive stuff for when I stumble upon a really good design.

I started using this DollarTree foam-board after watching Ed do his thing over at Experimental Airlines. He's had great success using this stuff.

Yeah sure I could buy expensive foam but at just $1 for a 20" x 30" sheet, I'm far more likely to experiment & have fun building goofy stuff than I would using the expensive foam. Besides this stuff is really pretty good. I'm quite impressed.

Stock with the paper on both sides, its very rigid. Remove one side & you can bend it into nice curved shapes. Take both sides off & you more or less have a sheet of crash-proof EPP kinda stuff. Its pretty versatile & unlike other foam-board, the paper peels off in one piece.

I picked up 20 sheets, enough for dozens of projects, for just $20. Gonna have some fun with it & see what I think. I'll save the expensive stuff for when I stumble upon a really good design.

Nodd, IMHO All of your Scratch Built Models are a Really Good Design Take care and have fun, Chellie

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL

I started using this DollarTree foam-board after watching Ed do his thing over at Experimental Airlines. He's had great success using this stuff.

Yeah sure I could buy expensive foam but at just $1 for a 20" x 30" sheet, I'm far more likely to experiment & have fun building goofy stuff than I would using the expensive foam. Besides this stuff is really pretty good. I'm quite impressed.

Stock with the paper on both sides, its very rigid. Remove one side & you can bend it into nice curved shapes. Take both sides off & you more or less have a sheet of crash-proof EPP kinda stuff. Its pretty versatile & unlike other foam-board, the paper peels off in one piece.

I picked up 20 sheets, enough for dozens of projects, for just $20. Gonna have some fun with it & see what I think. I'll save the expensive stuff for when I stumble upon a really good design.

Good point. I built a depron skinned wing once, just to experiment with the material. I had to talk myself into it, due to the high cost of the depron sheet. For a prototype experimental design, I wouldn't care to put all that money in depron sheet either, when a less expensive foam will do the job.
BTW I have the same gyro that you have, stashed away for if I ever get back on my 400 EXI. Big if. The heli guys claim it to be an excellent gyro for the price. I would be interested in knowing how a heading gyro compares to a rate gyro, for boating use.

Nodd, IMHO All of your Scratch Built Models are a Really Good Design Take care and have fun, Chellie

*smile* thanks Chellie.

Originally Posted by Bill G

BTW I have the same gyro that you have, stashed away for if I ever get back on my 400 EXI. Big if. The heli guys claim it to be an excellent gyro for the price. I would be interested in knowing how a heading gyro compares to a rate gyro, for boating use.

I believe my gyro can do both modes, heading or rate. I tried it out on a few airplanes in rate mode, did a fair job of keeping the wings level. I've seen YouTube videos of gyros used on boats & even an airboat that refused to go straight for more than 20 feet. They seemed pretty effective. Again though, I'll probably not need it but I think it'll be something fun to try.

Holes in my boat
The area where the motor pylon will mount needs to be water tight. I mixed up some epoxy & micro-balloons to cover the hardwood mounting blocks. Not wanting the epoxy to run into the bolt holes I threaded in some nylon bolts...

To insure I could get the bolts out again I coated them with some petroleum jelly (minds out of the gutter folks)...

Thankfully the jelly worked & the bolts came out no problem...

Spackling
Rather than add layer after layer of heavy, expensive resin to the fiberglass to get a nice finish, I've found that a couple of coats of watered down drywall spackling produces an awesome finish. Obviously it'll need sanding, right now you can still see the brush strokes...

Motor Pylon
I love finding stuff around the house to use in my projects. I had this old piece of U shaped aluminum that used to hold some weather stripping on the bottom of our screen door...

I cut a short length...

A few more cuts with the bandsaw...

That's starting to look a little like a motor pylon...

Used a template to get the angles right...

And there she is, a nice strong, lightweight custom motor pylon...

Tomorrow I hope to sand down the spackling & get some paint on the hull. Then I can start installing the fun stuff.

nodd, keep the pictures coming,she's looking really nicely designed and i'm enjoying following along your build on the air boat. hope you'll post a vid of it on the water using the rescue float bar when she's finished.

narrow is the place to land...wide is the space to crash....choose the narrow way!

Smooth
I sanded most of the spackling back to the fiberglass, love the way it fills in the cloth's weave. The foam-board has a slight waviness to it, so I have low spots every few inches. I slapped on more spackling in the low areas...

Once that was dry it was back to sanding...

Happy with that I sprayed on a coat of primer, looking pretty good for an el-cheapo foamy airboat...

Rudders
Well the hull is looking pretty true but at some point I'm going to want this thing to turn. So lets make my simple motor pylon more complicated...

Paint
I was all set on a nice simple red & white color scheme until I found myself ogling the cool color choices at the paint store. So this will not be a red & white airboat. Having laid down some gloss white last night, I started masking off the graphics...

When I saw this color on the shelf I just had to use it. That's some SERIOUS green...

The motor pylon gets a slightly saner green...

Although this paint dries to the touch in less than an hour, I want to wait until tomorrow before applying any masking tape on top of it. I learned the hard way, rushing a masking job only brings grief. Hope to finish the paint tomorrow then I can get on with the assembly.

While we wait for the paint to dry... I wasn't really happy with the photos I took of the pylon/rudder-hinge system. So I created this diagram that hopefully makes things a little clearer as to how that all works...

This diagram features an uncut U channel unlike mine that I hacked in half but that's how I'd do things if I'd had a wider U channel to work with.